1. Technical Field
The present disclosure relates to power storage devices used in various electronic devices, industrial equipment, automobile equipment, and the like, and relates to manufacturing methods thereof.
2. Description of the Related Art
As high-frequency electronic devices are increased, an electrolytic capacitor, which is one of power storage devices, is required to have large capacity and low equivalent series resistance (hereinafter, referred to as ESR) characteristics in high-frequency regions. Recently, in order to reduce ESR in such high-frequency regions, a solid electrolytic capacitor using, as an electrolyte, a solid electrolyte such as conductive polymers having higher electric conductivity than that of a conventional electrolytic solution, has been put into production. With respect to large-capacity demands for the solid electrolytic capacitor, winding-type solid electrolytic capacitors having a configuration in which interior of a capacitor element wound with a separator interposed between anode foil and cathode foil is filled with conductive polymers has been put into production.
However, the solid electrolytic capacitor as described above uses only a solid electrolyte, which has poor restorability to a dielectric oxide film, as an electrolyte. Therefore, compared with a conventional electrolytic capacitor using an electrolytic solution, increases in leakage current, or short-circuit failures caused along with defects of dielectric oxide film, etc. are likely to occur. Therefore, it is difficult to make a solid electrolytic capacitor having a high withstand voltage.
On the other hand, in order to improve the above described problem, an electrolytic capacitor utilizing, as an electrolyte, both of an electrolytic solution and a solid electrolyte formed by conductive polymers has been proposed. In this electrolytic capacitor, separator paper such as Manila paper or craft paper, a porous film, a synthetic-fiber unwoven fabric, or the like is used as a separator base material. Electrical conductivity is imparted to this separator base material by depositing conductive polymers on the separator base material. Then, a capacitor element is formed by interposing the separator to which electrical conductivity has been imparted (hereinafter, referred to as an electrically-conductive separator) between anode foil and cathode foil. The capacitor element formed in this manner is impregnated with the electrolytic solution (see Unexamined Japanese Patent Publication No. H7-283086, for example).